协议

接口文件1:Hunter.h

#import <Foundation/Foundation.h>
#import "TProtocol.h"

@interface Hunter : NSObject
@property (nonatomic,retain) id <TProtocol> animal;
- (void) hunt;

@end

实现文件1:Hunter.m

#import "Hunter.h"
#import "TProtocol.h"

@implementation Hunter
- (void) hunt
{
    if (_animal != nil)
    {
        [_animal catched];
    }
    if (_animal != nil && [_animal respondsToSelector:@selector(escape)])
    {
         [_animal escape];
    }
}
@end

 

接口文件2:Tiger.h

#import <Foundation/Foundation.h>
#import "TProtocol.h"

@interface Tiger : NSObject <TProtocol>
//- (void) catched;
//- (void) escape;

@end

实现文件2:Tiger.m

#import "Tiger.h"

@implementation Tiger : NSObject
- (void) catched
{
    NSLog(@"%s",__PRETTY_FUNCTION__);
}
- (void) escape
{
    NSLog(@"%s",__PRETTY_FUNCTION__);
}

@end

 

接口文件3:Dog.h

@interface Dog : NSObject <TProtocol>
- (void) catched;

@end

 

实现文件3:Dog.m

#import "Dog.h"

@implementation Dog
- (void) catched
{
    NSLog(@"%s",__PRETTY_FUNCTION__);
}

@end

 

 

接口文件4:TProtocol.h

#ifndef _008protocol_TProtocol_h
#define _008protocol_TProtocol_h
@protocol TProtocol <NSObject>
@required
- (void) catched;
@optional
- (void) escape;

@end
#endif

 

 

测试文件：main.m

#import <Foundation/Foundation.h>
#import "Hunter.h"
#import "Tiger.h"
#import "Dog.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool
    {
        Hunter *hunter = [[Hunter alloc] init];
        Tiger *tiger = [[Tiger alloc] init];
        Dog *dog = [[Dog alloc] init];
        
        hunter.animal = tiger;
        [hunter hunt];
        
        hunter.animal = dog;
        [hunter hunt];
    }
    return 0;
}